1. Field of the Invention
The present invention relates to a control device of a valve such as a throttle valve or an exhaust gas recirculation valve (EGR valve) installed in a fluid passage for performing air supply or gas exhaust with an engine.
2. Description of Related Art
A control device of a valve such as a throttle valve or an exhaust gas recirculation valve (EGR valve) installed in a fluid passage for performing air supply or gas exhaust with an engine performs deposit elimination operation with the valve in order to prevent malfunction due to deposits such as oil mist or soot adhering to a wall of the fluid passage.
The deposit elimination operation by the valve is performed by driving the valve across a fully-closed position of the valve when an influence of the operation of the valve over an operating state of the engine is very small, for example, when the engine is stopped. The valve is not only driven from the fully-closed position in a valve-opening direction but also driven from the fully-closed position in a valve-closing direction opposite to the valve-opening direction. Thus, the deposit on the fluid passage wall is scraped and eliminated (for example, as described in JP-A-2001-173464 or JP-A-2003-314377).
If the valve is driven near the fully-closed position, the valve and the fluid passage wall will rub against each other or excess torque will be applied to a gear portion of a motor that drives the valve. As a result, a noise will be caused. During a period suitable for the deposit elimination operation, engine rotation speed and engine torque are low and an engine noise is low, too. Therefore, the noise accompanying the deposit elimination operation reaches vehicle occupants and increases annoyance for the vehicle occupants.